- #1
talolard
- 125
- 0
Hello all. I have a question about determinants. The question is from an exam and solutions were not published. I would like to know if my solution is correct. Please excuse me for the imperfect formatting, I am struggling with the interface. Espeacially the superscripts were supposed to be subscripts.
The question is to compute the determinant of a matrix of polynomals of degree n-2 or less that looks like this:
F[tex]_{1}[/tex](X[tex]_{1}[/tex]) F[tex]_{1}[/tex](X[tex]_{2}[/tex]) ... F[tex]_{1}[/tex](X[tex]_{n}[/tex])
F[tex]_{2}[/tex](X[tex]_{1}[/tex]) F[tex]_{2}[/tex](X[tex]_{2}[/tex]) ... F[tex]_{2}[/tex](X[tex]_{n}[/tex])
[tex]\cdots[/tex]
[tex]\cdots[/tex]
[tex]\cdots[/tex]
F[tex]_{n}[/tex](X[tex]_{1}[/tex]) F[tex]_{n}[/tex](X[tex]_{2}[/tex]) ... F[tex]_{n}[/tex](X[tex]_{n}[/tex])I assumed n=3 and showed that in this case the determinant is 0.
I then assumed correctness for n and want to show that this is true for n+1 thus proving by induction.
Writing the same matrix but with n+1 rows and columns, I compute the determinant using expansion by row. I "crossed out" the n+1 row and n+1 column and so have a sum of sclars (which are polynomials) multiplying the NXN matrix that I assumed has a 0 determinant. So the sum is 0 hence conculding the proff.
Is this correct?
Thank you
Tal
Homework Statement
The question is to compute the determinant of a matrix of polynomals of degree n-2 or less that looks like this:
F[tex]_{1}[/tex](X[tex]_{1}[/tex]) F[tex]_{1}[/tex](X[tex]_{2}[/tex]) ... F[tex]_{1}[/tex](X[tex]_{n}[/tex])
F[tex]_{2}[/tex](X[tex]_{1}[/tex]) F[tex]_{2}[/tex](X[tex]_{2}[/tex]) ... F[tex]_{2}[/tex](X[tex]_{n}[/tex])
[tex]\cdots[/tex]
[tex]\cdots[/tex]
[tex]\cdots[/tex]
F[tex]_{n}[/tex](X[tex]_{1}[/tex]) F[tex]_{n}[/tex](X[tex]_{2}[/tex]) ... F[tex]_{n}[/tex](X[tex]_{n}[/tex])I assumed n=3 and showed that in this case the determinant is 0.
I then assumed correctness for n and want to show that this is true for n+1 thus proving by induction.
Writing the same matrix but with n+1 rows and columns, I compute the determinant using expansion by row. I "crossed out" the n+1 row and n+1 column and so have a sum of sclars (which are polynomials) multiplying the NXN matrix that I assumed has a 0 determinant. So the sum is 0 hence conculding the proff.
Is this correct?
Thank you
Tal